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Slide 2

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Identification of GASES Gas Appearance Density Solubility Collection Test for Equation Method GasHydrogen Colourless Less dense Almost insoluble Over water OR A pop is heard 2H(g) + O(g) than air in water upwards into when a lighted 2HO(l) (H) test tube OR into splint is held a gas syringe to the mouth of the tube.Oxygen Colourless Almost equal Only slightly Over water OR Will relight a _ density to air soluble in water into a gas syringe glowing splint (O)Carbon Colourless Denser than Only slightly Over water OR Limewater will Ca(OH)(aq) air soluble in water into gas syringe go cloudy +CO(g)Dioxide when CO is CaCO(s) + (CO) bubbled HO(l) through it: Forms calcium carbonate precipitateChlorine Green Denser than Quite soluble in Downwards into Will bleach _ air water test tube OR into damp litmus (Cl) gas syringe paperAmmonia Colourless Less dense Very soluble in Upwards into Alkaline so will _ than air water test tube OR into turn damp red (NH) gas syringe litmus paper blue.…read more

Slide 3

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Testing for WaterAnhydrous copper(II) sulfate Cobalt chloride paper· White solid (powder like) · This is filter paper that has been dipped in cobalt chloride solution and dried in a· When water is added it goes blue dessicator.· This is because dropping water onto it causes · A dessicator contains a substance thatit to form waters of crystallisation. absorbs water· The equation for this is: · When dry, the paper is blue. CuSO(s) + 5H0(l) CuSO·5H0(s) · Adding water turns it pink· The test works for anything that containswater BUT it does not show whether the water · The test works for anything that containsis pure. water BUT it does not show whether the water is pure. To check if a liquid is pure water, heat it until it boils which should be at 100 C at 1ATM…read more

Slide 4

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Testing for Cations (positive ions) Add NaOH Warm until just boiling solution. Does a NO and test with damp red litmus paper. Does it go precipitate form? blue? YES YES NO NH + Flame test ­ Using a fresh sample. dip a platinum or nichrome wire in HCl and hold in a Bunsen until no colour is given to the flame. The What colour is the wire is dipped back into the acid then into a precipitate? small sample of the solid being tested and returned to the flame. What colour is the flame? Brown/orange Lilac Green Blue Orange/red Red Orange (brick red)Fe 2+ Fe 3+ Na + Cu 2+ K+ Li + Ca 2+ The precipitates are the ion hydroxide e.g. Iron (II) hydroxide, Fe(OH)2…read more

Slide 5

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Testing for Anions (negative ions) Dissolve the solid. Add a few drops of dilute nitric acid and NO a few drops silver chloride solution and gently shake. Does a precipitate form? Dissolve a fresh sample of YES solid. Add a few drops of NO barium chloride solution and a few drops dilute HCl and shake. White Yellow Does a white precipitate form? Cream Dissolve a fresh sample of solid YES in HCl. Look for bubbles of gasCl - being produced. Collect gas Br - I- and bubble through limewater. SO 2- Does it go cloudy? The precipitates are the Silver ion e.g. Silver Chloride, AgCl Barium Sulfate forms. YES NO CO 2- Unknown First carbon dioxide and water form, then the carbon dioxide reacts with the limewater to form a precipitate of calcium carbonate.…read more